Sorry if you feel you're on a wild goose chase but I'm definitely seeing something, but not all the time.
I view it in the spirit of scientific enquiry. There is a point to be resolved, and I am not satisfied until there is clear indesputable evidence to resolve it.
Regarding thin black bars to the left and right, I think you should read
THIS (click).
I have prepared two 30-second test card MP4s - TestCard16x9 is a 1280x720 field ruled in squares with diagonal lines, and TestCard4x3 is a 640x480 field similarly ruled. If the TV is overscanning it will not show the grid lines at the border of the frame. The rules are a 16x9 or 12x9 grid respectively, so they should be squares. The diagonals will not be straight if there is non-linear distortion horizontally or vertically (but not if the horizontal and vertical distortions are the same).
The result of me displaying these via my HDR-FOX and HDMI to my Samsung 32EH5000, Samsung set to "Screen Fit" (ie no overscan), using any combination of test card and pillar box, zoom, or auto, is absolute linearity.
Case closed as far as I am concerned.
TestCard4x3.mp4
TestCard16x9.mp4
(Right-click and select "save target as", copy to USB and transfer to HDR-FOX.)
Here is what you should see (widescreen TV, ie 16:9, Humax video preferences set to 16:9):
- With overscan turned off (TV settings), TestCard16x9 shows a matrix of squares, 16 horizontal x 9 vertical, with a white edge all round. Diagonal lines meet at the edge of the frame The squares are of even size across the whole frame, and the horizontal, vertical, and diagonal lines are all straight (compare against a ruler). Changing the Humax "WIDE" button setting between "Pillar Box", "Zoom", and "Auto" makes no difference whatsoever.
- With overscan turned off (TV settings) and the Humax "WIDE" button set to "Pillar Box", TestCard4x3 shows a matrix of squares, 12 horizontal x 9 vertical, with a white edge all round. Diagonal lines meet at the white edge of the test card. The squares are of even size across the whole frame, and the horizontal, vertical, and diagonal lines are all straight (compare against a ruler).
- With overscan turned off (TV settings) and the Humax "WIDE" button set to "Auto", TestCard4x3 is stretched horizontally so that it now fills the TV frame, with the white edge visible all round. The "squares" are now rectangles and the diagonals are no longer at 45 degrees, but all the lines remain straight.
- With overscan turned off (TV settings) and the Humax "WIDE" button set to "Zoom", TestCard4x3 is stretched horizontally so that it now fills the TV frame, with the white edge visible at the left and right edges, and it is also stretched vertically so that the top and bottom portions of the test card are no longer visible. The squares remain squares and the lines are all straight.
- With overscan turned on (TV settings), the above results are similar except the edges of the test card exceed the edges of the TV frame (the white border is not visible and the diagonals do not meet at the edge of the frame). Overscan is the default TV setting for the internal tuner and typically TVs do not allow an overscan-off setting when using the tuner.
If during these tests the TV shows any non-linearity (the lines, including diagonals, are not straight and/or squares are not of even size across the whole frame), this is the fault of the TV or its settings. Some TVs have a "panoramic" setting, typically used to fit a 16:9 picture onto a 4:3 display by squashing the image horizontally progressively towards the edges.
If the TV shows no non-linearity but broadcasts appear to be non-linear, this must be due to the broadcast itself. The camera in use could be fitted with a wide-angle or anamorphic lens - these distort the image in a non-linear way.
To view Humax output (recorded or live) in the same way as the TV would have displayed it from its own tuner, the TV must be set to overscan on the HDMI input. Broadcasters appear to expect an overscan region and do not always provide picture content right up to the edge. On the other hand, for the best possible HiDef picture (mapping the content pixels exactly with the TV screen pixels without interpolation) it is necessary to turn overscan off.